Can I explain how Sakura did to marry Sasuke? And how was Madara apparently single despite being one of the strongest of her clan in her time? In ancient era, in the middle of the war, carrying a courtship and weddings was very complicated, so I imagined that the Uchiha clan decided to opt with simple practices; It occurred to me a simple practice in which women interested in a man, assert themselves with a challenge on their part, challenging their loving interest to a duel where they have to win and convince him to exchange sake glasses to "marry" with this person. Sakura with his great strength and strategy could have been able to beat Sasuke once or maybe Sasuke let himself win. But that would also explain that Madara was apparently single, being one of the leaders of the clan and the most powerful, continuing with his lineage should be a priority, but I suppose he was not very interested in that or perhaps there was no woman who could win against him (in addition that his obsession with fighting with Hashirama and his pesmist attitude, let's say didnt help him much)